Tests will be carried out this morning to determine whether chemicals have been successful in treating the problem.

Mr Palmer says the mussel prefers closed, marina-type environments, and there are none for a long distance outside the Darwin area.

"The closest one I understand, [a] lock-up marina, is in Carnarvon in Western Australia and I think you're down as far as Noosa on the Queensland coast before you come across another lock-up marina," he said.

"So it would appear that although we've got the infestation here, the risk to those other areas may well be minimised by the lack of similar and like environments."